The measurement of electro-optical properties of optoelectronic components generally takes place according to the prior art by applying a DC voltage to the optoelectronic component. Occasionally, optoelectronic components are at least temporarily present in a form in which their connections are short-circuited, that is to say in which there is a negligible ohmic resistance between their connections. This is the case particularly if optoelectronic components are arranged on a connection board, e.g., during the production of optoelectronic components. For example, optoelectronic components are mounted in a metallic lead frame composite, as a result of which the contacts of the optoelectronic components are short-circuited with respect to DC voltages. Consequently, these cannot be operated with DC current in order to determine their electro-optical properties for the purpose of process monitoring and/or process control.
While the optoelectronic components are singulated and provided with individually contactable connections at the end of the production process, it may be advantageous for the components not yet to be singulated and/or not yet to be made individually contactable at least during sub-steps of the production process. However, it is desirable to be able to measure electro-optical properties of the optoelectronic components even in such a state, for example, in order to pre-sort or to optimize the optoelectronic components and/or in order to adapt further production steps to the measured electro-optical properties. As a result, the rejects are reduced, thus affording a saving of time and costs.
In particular, the time required by lengthy production steps such as the curing of a conversion material, for example, can be better utilized. During the production of light emitting diodes, e.g., light emitting diodes which emit white light on the basis of volume conversion, the concentration and filling quantity of the conversion material are subject to fluctuations of varying magnitudes on account of current production methods. At present, in the manner of random sampling, an optoelectronic component is singulated and measured after the potting and baking of the material and can no longer be used for further production steps such as a plating step, for example.
DE 102013102322.3 discloses a method for measuring at least one optoelectronic component arranged on a connection board, which comprises exciting at least one electromagnetic resonant circuit, which is formed by the at least one optoelectronic component and the connection board, such that the at least one optoelectronic component is excited to emit electromagnetic radiation, and measuring at least one electro-optical property of the at least one optoelectronic component. The excitation of the electromagnetic resonant circuit can take place by inducing an electrical alternating voltage in the electromagnetic resonant circuit by generating a temporally variable electromagnetic alternating field. The inductive excitation has the advantage here that the excitation can take place in a contactless manner. The temporally variable electromagnetic alternating field can be generated, e.g., by an inductive element, in particular a coil with one or more turns.
By means of the method described in DE 102013102322.3, short-circuited optoelectronic components in a lead frame composite can be excited to emit light. However, if many optoelectronic components are connected in parallel, as is typical of many constructions, multiple optoelectronic components emit light simultaneously upon inductive excitation with a conventional coil design. A selective measurement, e.g., of the colour, of individual optoelectronic components is thus impossible.
In other constructions, the optoelectronic components to be measured are assigned to comparatively small regions in which an electromagnetic resonant circuit can be induced by the method described in DE 102013102322.3. In this case, comparatively high magnetic field densities are needed to excite the individual optoelectronic components to emit light. In many cases, it is very difficult to achieve the required field density using wire coils which have a conventional geometry in terms of their winding. Moreover, a coil design is desired in which the coils can be produced reproducibly and inexpensively even on a small scale